The invention relates to a hoisting apparatus comprising a frame, a rope drum provided with a groove, a hoisting motor, a gear and a pinion in such a way that the hoisting motor is at least partly positioned inside the rope drum supported against the frame by its both ends, and that the hoisting motor and the gear are supported against the frame only by one end of the rope drum, by which end the hoisting motor and the gear are arranged to rotate the rope drum via the pinion.
The hoisting apparatus is generally a part of a rope hoist which is either fixedly mounted or moving along a track by means of a trolley. The hoisting apparatus can also be used as such to lift a load. In rope hoists intended for vertical transfer of a load, the length of the hoisting apparatus is a significant problem because it limits the travel of the trolley. The great length of the hoisting apparatus results from the basic idea of the rope hoist design, i.e. the tendency to minimize the diameter of the rope drum to optimize the force-transmitting gear, which leads to the great length of the rope drum and in this way of the whole rope hoist with hoisting heights and rope reevings commonly in use. Due to the tendency to minimize the diameter of the rope drum, the intention has typically been to dimension the ratio of the pitch circle diameter of the rope drum, i.e. the diameter of the centre of the groove, to the diameter of the hoisting rope to correspond to the standard minimum requirements in the most common utilization categories of existing rope hoists. Therefore, the ratio of the pitch circle diameter of the rope drum to the diameter of the hoisting rope is typically 16-25, depending on the intensity of use, whereby the length of the rope drum is significantly greater than the diameter of the rope drum. Since the length of the rope drum is the main factor in the total length of the hoisting apparatus and the whole rope hoist and since the direction of travel of the rope hoist mounted on the trolley is generally parallel to the longitudinal axis of the rope drum, the length of the rope drum is a significant problem because it limits the travel of the trolley. Further, the movement of the departure point of the hoisting rope on a long rope drum in the direction of the longitudinal axis of the rope drum during the rotational movement of the rope drum is great. In rope hoists with multiple ropes, when the departure point of the hoisting rope is displaced, i.e. when it drifts, the angle of departure of the hoisting rope leaving the rope drum changes relative to the longitudinal axis of the rope drum. The greater the drift and the more multiple the rope reeving, the greater the change in the angle of departure. Depending on the type of the rope, the maximum value of the angle of departure is 1.5xc2x0 to 4xc2x0. When the maximum value is approached or exceeded, the hoisting rope wear is increased. Extensive drift of the hoisting rope can cause problems in the control of the load and result in a tendency of the hoisting hook to twist. The drift of the hoisting rope also causes problems in optimizing load-bearing structures, as the supporting forces vary depending on the departure point of the hoisting rope from the drum.
The known solutions to minimize the length of the hoisting apparatus include positioning either the hoisting motor or the gear or both as well as the pinion inside the rope drum, or positioning the hoisting motor beside the rope drum. According to the first alternative, the shortest length of the hoisting apparatus has been achieved by positioning the hoisting motor, the gear and the pinion inside the rope drum in the direction of the longitudinal axis of the rope drum; however, as the diameter of the rope drum is as small as possible, this solution causes the hoisting motor to heat intensively due to the small cooling space. The structure also requires a firm frame at both ends of the rope drum and an intermediate shaft exposed to vibration between the hoisting motor and the gear. Positioning the hoisting motor beside the rope drum increases the width of the rope hoist, but the total length of the rope hoist is still determined on the basis of the length of the rope drum.
An object of this invention is to provide a hoisting apparatus of a new type, short in the longitudinal direction.
The hoisting apparatus according to the invention is characterized in that the pinion is positioned between a cylinder, which is parallel to the longitudinal axis of the rope drum and defined by the housing of the hoisting motor, and the rope drum.
An essential idea of the invention is that in the hoisting apparatus intended for vertical transfer of a load, the hoisting motor is at least partly positioned inside the rope drum supported against the frame of the hoisting apparatus by both ends thereof, and that the hoisting motor and the gear transmitting force from the hoisting motor to the pinion is supported against the frame by only one end of the rope drum, by which end the hoisting motor and the gear are arranged to rotate the rope drum via a pinion positioned between a cylinder, which is parallel to the longitudinal axis of the rope drum and defined by the housing of the hoisting motor, and the rope drum. According to a preferred embodiment of the invention, the diameter of the rope drum is significantly greater than the diameter of the hoisting motor. According to a second preferred embodiment of the invention, the hoisting motor is positioned inside the rope drum asymmetrically relative to the centre of the rope drum. According to a third preferred embodiment of the invention, the torque required for the rotation of the rope drum is transmitted to the rope drum via the periphery thereof at the departure point of the hoisting rope from the rope drum.
An advantage of the invention is that the outer dimensions of the hoisting apparatus and in this way of the whole rope hoist are small in the direction of the longitudinal axis of the rope drum. Owing to the significantly greater diameter of the rope drum compared with the known solutions, it is possible, while the hoisting height remains constant, to use a significantly shorter rope drum. Owing to this, the horizontal movement of the hoisting rope in connection with the hoisting or lowering of a load is small, and detrimental horizontal movement of the load is thus decreased. Owing to the small horizontal movement of the hoisting rope, the rope force is divided almost evenly over the load-bearing structures, enabling small and light supporting structures, which can further be utilized in the dimensioning of the trolley of the rope hoist and of the bridge girder supporting it. Since the angle of departure of the hoisting rope from the rope drum is small and since the ratio of the pitch circle diameter of the rope drum to the diameter of the rope can be dimensioned up to 2- to 3-fold compared with the minimum values commonly in use and allowed by the standards, the durability of the rope is significantly increased. Furthermore, the small horizontal movement of the hoisting rope and the small rope angle together efficiently reduce the twisting risk of the hoisting hook supported by the rope. Owing to the small horizontal movement of the hoisting rope, the hoisting apparatus according to the invention allows construction of a rope hoist with up to 12-fold rope reeving without exceeding the rope angle of 4xc2x0. Since the inner diameter of the rope drum is significantly greater than the outer diameter of the hoisting motor and since the hoisting motor and the gear are supported against the frame by only one end of the rope drum, it is possible to arrange better ventilation for the hoisting motor compared with a hoisting motor positioned outside the rope drum, whereby there are no problems with the heating of the hoisting motor. A further advantage is that the structure is easy to modulate because the length of the rope drum does not affect the supporting of the hoisting motor and the gear attached thereto. Positioning the hoisting motor asymmetrically relative to the centre of the rope drum allows the gear to be designed more freely. Further, when the torque required for rotating the rope drum is transmitted to the rope drum via the periphery thereof at the departure point of the hoisting rope from the drum, the dimensioning of the hoisting motor of the hoisting apparatus and of the gear attached thereto can be optimized, and the hoisting height can be changed by changing either the diameter or the length of the rope drum.